Method for uv photolytic separation of pollutant gases from an emission stream

ABSTRACT

A method and apparatus for separating gaseous emission pollutants from a scrubber by using a narrow band of UV light energy emitted from an LED light source. The method includes sweeping the evolved gas away from the flow of liquid containing the pollutant using a non-reactive gas. The pollutant can be CO 2 , NO x , SO x , or other pollutants. The method can operate on multiple pollutants the gas stream, using different banks of LEDs, specifically tuned for a certain pollutant.

PRIORITY/CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/335,821, filed Jan. 13, 2010, the disclosure of which is incorporatedby reference.

TECHNICAL FIELD

The present invention generally relates to methods for removingpollutants from emission streams, and more particularly by use of UVlight generated by LED sources in a narrow bandwidth to efficientlyseparate and remove pollutants of an emission streams from a scrubber.

BACKGROUND

Coal-fired plants equipped with the latest thermal process to extractcarbon dioxide (CO₂) burn 30% more coal than plants that do not extractCO₂. CO₂ capture requires more coal because it creates a 24% parasiticenergy demand by CO₂ absorption, desorption, and compression unitoperations. Because of this huge added cost, coal-fired plants areresistant to adding CO₂ capture technology.

Several international treaties on the Earth's climate at Montreal,Kyoto, and Copenhagen have demonstrated the importance of globalregulation of emissions of greenhouse gases, particularly CO₂. Accordingto the EPA, the process of generating electricity is the single largestsource of CO₂ emissions in the United States, representing 41% of allCO₂ emissions, with over 80% of the CO₂ from electricity generationcoming from coal-fired power plants. Unfortunately, coal will continueto be used as a major source of power generation in the U.S. for theforeseeable future, and according to the World Coal Institute, coal'sshare in global electricity generation is set to increase from 41% to44% by 2030. With this in mind, reducing the environmental impacts ofcoal, especially CO₂, is vital, and capturing CO₂ in the most efficientand cost effective manner is critical for the industry.

Two major reviews in 2009 discussed the three CO₂ capture concepts forcoal-fired power plants—(a) post-combustion capture, (b) oxy-combustioncapture, and (c) pre-combustion capture; with the post-combustioncapture technology being the most efficient, cost effective, and mostadopted today. There are four major categories of current technologiesfor post-combustion CO₂ capture. These are (i) amine absorption; (ii)reactive oxide/carbonate solids; (iii) zeolite absorption, and (iv)membranes. The challenges for adoption of each of these technologieshave been discussed by Rochelle et al. in 2009. Amine absorption of CO₂is the most advanced, most well understood, and most successful method,with monoethanolamine (MEA) as the most widely deployed amine in CO₂capture in the industry. The United States Department of Energy alsoconsiders the amine solvent process as the current state-of-the-art incapture technology. Unfortunately, even using the MEA technologydramatically drops a power plant's overall thermal efficiency from 39%to 29%. In an amine solvent process, CO₂ is readily absorbed by an aminesolution from flue gas. However, thermally extracting the CO₂ from theamine solution is energy intensive and incurs burning 30% more coal thanis necessary to generate electricity. The thermal process increases thecost of electricity (COE) by 81% for a supercritical pulverized coalplant. The bulk of this parasitic energy is used for maintaining steamboilers that provide 100-120° C. temperature for thermal desorption ofCO₂ from an amine scrubber.

Recently, using Dow Chemical Company's 30% MEA for scrubber/separationprocesses of CO₂ capture has produced better efficiencies than with 20%MEA of Kerr-McGee, by reducing the amount of energy expended from 0.51to 0.37 megawatt-hours (MWh) per metric ton of CO₂ removed. The decreasein required energy has reduced the cost for the removal of CO₂ from $82to $51 per ton, but has still left us with an increase in the COE of81%. The photochemical CO₂ separation technology in this proposal hasthe potential to reduce the COE to 35%. This is significant for reachingthe goal of less than 35% COE. A review by Ramezan et al. has concludedthat this incremental improvement to the thermal process has yet to comeclose to achieving the DOE goal (and potentially EPA's regulatorystandard) of 90% CO₂ removal with less than a 35% increase in COE. Thephotolysis process has the potential to meet this goal.

SUMMARY OF THE DISCLOSURE

The purpose of the Abstract is to enable the public, and especially thescientists, engineers, and practitioners in the art who are not familiarwith patent or legal terms or phraseology, to determine quickly from acursory inspection, the nature and essence of the technical disclosureof the application. The Abstract is neither intended to define theinventive concept(s) of the application, which is measured by theclaims, nor is it intended to be limiting as to the scope of theinventive concept(s) in any way.

Still other features and advantages of the presently disclosed andclaimed inventive concept(s) will become readily apparent to thoseskilled in this art from the following detailed description describingpreferred embodiments of the inventive concept(s), simply by way ofillustration of the best mode contemplated by carrying out the inventiveconcept(s). As will be realized, the inventive concept(s) is capable ofmodification in various obvious respects all without departing from theinventive concept(s). Accordingly, the drawings and description of thepreferred embodiments are to be regarded as illustrative in nature, andnot as restrictive in nature.

The disclosed technology addresses the need for reduction of greenhousegases by a transformative and new photolytic technology to replace thecurrent less efficient thermal process for capturing CO₂ emissions fromcombustion processes of coal-fired power plants. Additionally, thedisclosed technology is useful to separate other pollutants fromemission streams. The emission streams can be power plants, internalcombustion engines, or other sources of pollutants in emissions.

The photolytic process has the potential to dramatically cut the 30%increase in coal usage by more than half, a dramatic reduction that willsignificantly reduce the cost of capturing CO₂ and improve theacceptance of carbon capture by companies that operate coal-firedplants. The disclosed technology has capacity to capture more than 90%of the six to ten thousand tons per day of CO₂ produced by a 500 MWecoal-fired power plant, as an example.

One aspect of the disclosed technology transforms the currentstate-of-the-art MEA technology by replacing the current energyparasitic thermal processes with a photochemical process. Photolysis isan innovative and novel alternative source of energy using UV photons.Studies have shown that photolysis, providing energy in the form ofphotons, can effectively replace the thermal process with a significantreduction in required energy and with efficiency comparable to thecurrent thermal MEA technology for CO₂ desorption in a continuousprocess. The disclosed technology reduces the parasitic COE to less than50% of the current burden. Research has shown that photochemicalreactions are several orders of magnitude faster and use significantlyless energy than conductive thermal processes. As a result, someindustries, like the manufacture of photoresist in microelectroniccomponents, are using ultraviolet light emitting diodes (UV LEDs) topower energy efficient and effective photochemical processes.

The disclosed photochemical technology has two additional significantbenefits. First, it builds on the state-of-the-art MEA technology.Second, since it replaces only the thermal process in MEA technology, ithas the potential to be cost effectively retrofitted into existingplants with minimal down time.

The state-of-the-art MEA technology can be described as follows; MEAselectively absorbs CO₂ to a maximum 0.542 molCO₂/molMEA and is thensent to a stripper. In the stripper, the CO₂-rich MEA solution is heatedto 120-150° C. in a desorption chamber to release almost pure CO₂. TheCO₂-lean MEA solution is then recycled to the absorber. There have beenonly two commercial MEA-absorber processes since the 1970s; that is (i)a 20% MEA solution by Kerr-McGee used primarily with coal-fired boilers;and (ii) a 30% MEA solution by Dow Chemical used primarily on naturalgas fired plants. Both the 20% and 30% MEA solutions have become thestandard for CO₂ capture from power plant flues and both are used atinstallations worldwide. FIG. 1 illustrates the prior art processes of apulverized coal power plant without CO₂ capture and FIG. 2 illustratesthe prior art amine-absorption/thermal separation for scrubbing CO₂capture. As FIG. 2 implies, the amine plant is usually a separate unitlocated in the power facility.

Prior studies have shown that it could take as little as 43 kWh tocapture 1 t CO₂. A typical power plant without carbon capture produces 1t CO₂ for every 1200 kWh of net power generated. The theoretical minimumenergy requirement for the DOE standard of 90% CO₂ separation (as apercentage of net power production) is: [43 kWh/t of CO₂ captured]×[9 tcaptured/10 t produced]/[1200 kWh/t CO₂ produced]=3.2%. However, theestimated actual parasitic load of the CO₂ separation system is 16%,which is 5 times more than the minimum required 3.2% of the powerproduced. For the thermal process, 16% of the total output of 1200 kWh/tCO₂ produced, (i.e., 0.16×1200 kWh=168 kWh) is required to separate 1 tCO₂ from CO₂-rich MEA. By comparison the disclosed technology canconvert 1 kWh of electrical power input to more than 11.6 kWh photonenergy output for the CO₂ separation process (see legend of Table 1).Table 1 shows a comparison of energy required for thermolysis andphotolytic CO₂ separation. The actual parasitic loading for aphotochemical separation process will be 1/11.6 of amount currently usedby the thermal process.

TABLE 1 Comparison of energy required for thermal & photochemicalseparation & compression of CO₂ Thermal/MEA-technologyPhotochemical/MEA-technology Properties % of parasite energy 16%[(1/11.6) × 62] = 5.63% Potential total % COE 81% 35.11% (= 43.35/100 ×81) Constituent processes % required for CO₂ 62% 5.35% (photolysisreduced %) Separation % required for CO₂ 33% 33% compression % requiredfor Flue draft  5%  5% blower Total 100%  43.35%   Energy/potentialenergy 16% of 1200 kWh CO₂ = 168 kWh 46.8 kWh (electrical, LED) can beexpended to separate 1 t (or 0.17 MWh) heat used to generate 0.542 MWhCO₂ energy of steam photon energy Footnote: According the specificationof state-of-the-art LC-L3 UV-LED from HAHMAMTSU: UV intensity = 4600mW/cm² = 4600/1000/1000 = 0.0046 kW/cm². Output power = (0.0046kW/cm²/s) × (365 d × 24 h) = 40.296 kWh/cm² At 22.4 fold (bycollimation), the output power = (22.4) × (40.296) = 902.6304 kWh/cm²Power input (max.) = (80/1000) × (356 × 24) = 700.8 kWh Efficiency =902.6304/700.8 = 1.288/cm². According to HAMAMATSU specifications theimpact area of the LC-L3 UV-LED is 9 cm². This means that the efficiency= 1.288/cm² × 9 cm² = 11.6. The equivalent efficiency for the thermalprocess = 2.2.

The parasitic power demand of the thermal CO₂ separation process resultsin 81% increase in the Cost of Electricity (COE). There are three partsto the parasitic power demand; the thermal CO₂ separation process, theCO₂ compression process, and the draft blowers for the flue gas. Thethermal CO₂ separation process requires 62% of the parasitic energy, theCO₂ compression process uses 33%, and the draft blowers require 5%.According to HAMAMATSU LED specifications, 1 kWh of electricity willcreate 11.6 kWh of photon energy. Applying this to the parasitic energyrequired for thermal CO₂ separation leads to the conclusion that 1/11.6of 62% of the parasitic energy required for thermal CO₂ separationequals only 5.35%, the new, reduced requirement for CO₂ separation usingan LED UV source. Applying this new percentage to the COE for CO₂separation, reduces the increase in the COE from 81% for the thermalprocess, to only 43.4%, a decrease of 37.6% (33% for compression plus 5%for blowers plus 5.35% for separation equals 43.35%).

By using available efficiencies of electricity powered UV generation,the disclosed photochemical technology has the potential to cut theparasitic power demands of the current thermal technology by almosthalf; from 16% to only 9.1%. This will reduce the cost of removing a tonof CO₂ from the current efficiency at $51/t to only about $35/t of CO₂separated.

In typical photochemical reactions, a molecule gains the necessaryactivation energy to undergoing change by absorbing monochromatic ornon-monochromatic UV irradiation (releasing photon energy) from a lightsource see FIG. 3. Absorbed photons can (i) bring the molecule to thenecessary activation energy, or (ii) change the symmetry of themolecule's electronic configuration, in order to enable an otherwiseinaccessible reaction path. Successful application of photolytictechnology to large scale photolysis is dependent on (i) the intensitythe UV irradiation and (ii) the molar absorptivity of absorbing speciesin a process. The rate of reaction “I” is the number of photons absorbedper unit time and unit. However, I, appears is the Beer-Lambert-Bouguer(BLB) law relating incident, I₁, and transmitted light intensity, I_(o),path length, l, and concentration, c:¹¹

I ₁ e-^(klc) =I _(o)×10-^(εcl)  (Eqn. 1)

However, due to very high concentration of CO₂ absorption by 20% and 30%aqueous MEA absorbers, there may be a concern on the part of thereviewers that the UV absorption by the CO₂ separation process may notstrictly follow the BLB law. Therefore, the next three subsectionsdiscuss large scale industrial applications of UV irradiation, CO₂separation from carbamate in the literature, and a preliminary analysisdemonstrate that CO₂ is desorbed from a 20% amine when exposed to UVradiation.

INDUSTRIAL APPLICATIONS

For years there have been large-scale applications of photochemistry inthe cleaning of chlorinated compounds from public swimming pools and inthe treatment of dissolved dyes in industrial effluent of the textileindustry. More recently, studies of photodissociation of insecticidecarbamates to form free amine and CO₂, much like the disclosedtechnology, has been successful and has shown that photolysis occurs atfaster rate than the thermolysis or hydrolysis. These studies wereconducted using UV generators with only a fraction of the quantumefficiency of current LED generators (see Table 2). Table 2 show thephoton output and quantum efficiency of UV lamp generation sources andthe obvious higher efficiency of the LEDs.

Recently, LEDs—the most powerful artificial UV generators—have beenapplied on a large scale in the microelectronic industry as aphotoinitiator. Efficiency requirement of the microelectronics industryhas resulted in the development of ever-increasing LEDs power densities,currently at about 4600 mW/cm². Generally, the photolytic dissociationof amine carbamates, like NH₃—CO₂, has been achieved by application ofUV light at 290-360 nm wavelengths—this coincides directly with highbrightness UV LEDs based on the AlInGaN materials system. FIG. 4 showsthat significant advancement was achieved in the last three decades, andstrongly suggests more can be anticipated. Table 2—Comparison ofconversion (photon/electrical energy) efficiency of select UV sources.

The disclosed technology also utilizes a high intensity UV LED array,leveraging the significant recent advancement in high-brightness LEDs.As a result, photolytic technology will only get more efficient and morecost effective with time.

Photolytic Separation of CO₂ from Amine Carbamates in the Literature

A study done by Cameron, et al, the photolysis of3′,5′-dimethoxybenzoincyclohexyl carbamates to free cyclohexylamine andcarbon dioxide was achieved by using Rayonet lamp for generation of UVirradiation at =350 nm, with conversions was as high as 92-98%.

The study clearly showed that the time required for CO₂ desorption was afunction of absorption of UV irradiation vs. carbamate concentration.For example, photolysis of 38.6×10⁻³ M solution3′,5′-dimethoxybenzoincyclohexyl carbamates to cyclohexamine and CO₂,with 98% yield was accomplished in 90 minutes; and the same process fora 6.16×10⁻⁵ M solution produced 98% yield in 9 minutes. The results ofthis study suggest strongly that photolysis will be able to de-absorbover 90% of the CO₂ from an aqueous MEA solution in a continuousprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a prior art coal power plant without CO2 capture.

FIG. 2 is a diagram of a prior art coal power plant with MEA technologyfor CO2 capture, showing the parasitic energy process.

FIG. 3 is a diagram of Beer-Lambert-Bouguer absorption of a beam oflight as it travels through a medium of width I.

FIG. 4 is a graph showing the increasing output and efficiency ofdifferent types of LED technologies.

FIG. 5 shows the setup to verify photolytic CO2 separation from aqueousMEA.

FIG. 6 show different overlapping LED structures.

FIG. 7 shows energy intensity as related to photon travel distance.

FIG. 8 is a design of a prior art UV water purification device.

FIG. 9 is a graph showing the typical electroluminescence spectrum from415 nm solid state LEDs.

FIG. 10 is a graph of the spectrum of high pressure lamps, showingseveral energy peaks.

FIG. 11 is a view of a process design of the disclosed technology.

DEFINITIONS

In the following description and in the figures, like elements areidentified with like reference numerals.

The use of “e.g.,” “etc,” and “or” indicates non-exclusive alternativeswithout limitation unless otherwise noted.

The use of “including” means “including, but not limited to,” unlessotherwise noted.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

While the presently disclosed inventive concept(s) is susceptible ofvarious modifications and alternative constructions, certain illustratedembodiments thereof have been shown in the drawings and will bedescribed below in detail. It should be understood, however, that thereis no intention to limit the inventive concept(s) to the specific formdisclosed, but, on the contrary, the presently disclosed and claimedinventive concept(s) is to cover all modifications, alternativeconstructions, and equivalents falling within the spirit and scope ofthe inventive concept(s) as defined in the claims.

Prior Photolytic CO₂ Separation from (MEA)₂-CO₂

The disclosed technology discusses separation of CO₂ from scrubber ofpower plant emission streams as an example, but it is to be understoodthat this application of the technology is merely one example ofpossible applications, and is currently a preferred embodiment. Patentlaw requires that at least one preferred embodiment be listed, but thatthe invention is defined by the claims, not the disclosed preferredembodiment. After the application is filed, the preferred embodiment maychange, and thus the claims are the appropriate reference for theclaimed technology. Other possible emission streams include internalcombustion engine emissions, and any emission source which containspollutants. The pollutant addressed in the preferred embodiment is CO₂,but it is to be understood that other pollutants may also be removedfrom emissions streams, such as SO_(x), NO_(x), or other pollutants.

Shown in FIG. 1 is a coal power plant without CO₂ retracted. Thisinformation is prior art and is adapted from a publication of the UnitedStates Department of Energy's National Energy Technology Laboratory (USDOE NETL). A fluid air from a power plant enters the system at 112. Itgoes through a forced draft fan at 114 and through an air heater at 116.The warmed air is mixed with coal 118 and is burned in a furnace 120.The furnace has a convection section 122 and a radiant section 124. Aneffluent stream 126 exits the furnace 120 and flows through the airheater 116 through a precipitator 128 through an induced draft fan 130from which it is bubbled through an SO₂ scrubber 132. From the SO₂scrubber 132 slurry 134 is recovered, and effluent exits the stack 136.Lime slurry is added to the SO₂ scrubber. From the furnace 120, airpasses through a convection section 122 and a radiant section 1245, andat 126 exits the furnace. It again passes through the air heater 116,and through a precipitator 128, through an induced draft fan 130, and toan SO2 scrubber 132. Slurry exits the scrubber at 134, and lime slurryis added at 138. Gasses exit at stack 136. Another flow of gasses exitsthe furnace 120 and goes to steam turbines 140, to condenser 142 andwater heaters 144. Effluent gasses are routed back to the furnace 120via line 146.

The amine plant is shown in FIG. 2. There, MEA absorbs CO₂ throughchemical reaction in an absorber column. This reaction is reversible,and CO₂ is currently separated by heating the CO₂-rich amine in astripper column. The MEA may be recycled through the process.

FIG. 2 shows a coal powered plant with MEA technology for CO₂ capture.This shows the parasitic energy process of the prior art. The coal firedpower plant of FIG. 2 has the same components as shown in FIG. 1 exceptfor the region after the SO₂ scrubber 132. After the SO₂ scrubber 132 isan amine plant 148 which includes a heater, and in which CO₂ gas isevolved. CO₂ gas is collected and concentrated at 150 with the MEA beingreturned to the recycle system at line 152.

FIG. 3 shows a diagram of Beer-Lambert-Bouguer (BLB) absorption of abeam of light as it travels through a medium of width I. Thisillustrates that the fraction of light that transmits through a mediumis a function of the absorbing coefficient and the width.

FIG. 4 shows historical efficiency improvements of LED technologiessince 1960-2000. The X axis shows performance in lumens per watt. The Yaxis shows time in years. Shown are the improvements in gallium basedLEDs in curve 154. Improvements in molecular solid LED are shown in line156. Improvements in polymer LEDs are shown in line 158. Improvement innitride LEDs are shown in line 160. Improvements in InGn LEDs are shownin line 162.

FIG. 5 shows the setup to verify photolytic CO₂ separation from aqueousMEA solution. Shown are LED generators of monochromatic UV at =365,shown at 30. FIG. 5 also includes an FTIR spectrometer at 32. MEA-CO₂ ata 20% solution of MEA is injected into the FTIR spectrometer at 34.Energy from the LED generator 30 causes CO₂ evolution from the MEA gaswith the CO₂ shown originating at 36.

FIG. 6 shows three views of LED generated light intensities and patternsfrom different arrangements of LED arrays. Shown on the left of FIG. 6is an LED array in which no lens is utilized to focus the light from theLED bulbs. The middle picture shows a tighter beam of light whichresults from the use of reflectors or optics to focus and overlap thelight from different LED light sources. LEDs are spontaneous emissiondevices, with a spatial emission pattern leading that is generallyLambertian without external optics, as illustrated in FIG. 6. In orderto improve the working distance from the light source to the illuminatedtarget, an array of LED lenses produce a collimated beam of higherintensity. Gradually expanding beams and overlap combining beam arraysproduce 7-fold and 22.4-fold increase in intensity of UV lightirradiation from three LEDs in an array (see FIG. 6). The energy densitywill depend on the photon travel distance, and on whether a lens wasused to focus the irradiation from arrays of LEDs or not—see FIG. 7.These factors are adjustable depending on the desired application.

FIG. 7 shows the irradiance from LEDs as it is affected by the workingdistance the use of the lens or no lens. The x axis shows irradiance inmW/Cm² and the y axis shows the working distance in centimeters. Theline 38 shows the irradiance when no lens is used, and as would beexpected, the irradiance drops off quickly as the working distancebecomes greater. Curve 40 shows the irradiance when light from an LED isfocused into a parallel beam. As can be see the drop off irradiance ismuch less pronounced as the working distance increases. Curve 42 showsthe affect of combining the light output of several LEDs by overlappingthem onto a target. The graph shows that there is an optimum workingdistance with the irradiance dropping off rapidly from the optimumworking distance of approximately 8 centimeters.

FIG. 8 shows prior art design of a UV water purification unit 44. Theunit 44 includes an inlet 46 and an outlet 48 an ultra violet source 50in the form of a tube or rod, a chamber 52 and a liquid medium 54. Thiskind of device typically uses a germicidal lamp in a quart sleeve, andis built for the purpose of killing microbes by exposure to UV light.

FIG. 9 shows an example of the generation of UV light from an LED with apeak of about 20 nm. By comparison FIG. 10 shows the production ofenergy from a mercury bulb, which contains a series of peaks throughoutthe UV tube visible spectrum region. In FIG. 9 the x axis showsintensity and the y axis shows wavelength in nm. FIG. 10 shows relativespectral power on the y axis and the wavelength in nanometers on they-axis.

FIG. 11 shows a preferred set up for treatment of pollutants such as CO₂from an effluent stream, with the method designated as 10. CO₂ rich MEAfrom an absorption chamber enters a separation chamber 12 at inlet 14. Afan 16 moves the CO₂ rich MEA at 18 over a UV LED panel 20. The UV fromthe LED panel 20 energizes the dissolved CO₂ in the MEA, and drives itoff as a gas, with the CO₂ entering a collection chamber 22 where it maybe routed to collection facilities at 24 or to analysis 26. Shown inFIG. 11 is a single LED panel which would be calibrated to provide anarrow band of energy for a specific pollutant, such as CO2, but otherdesigns could have multiple LED panels in series, with each onecalibrated for a specific pollutant and the most effective wavelengthfor that pollutant. Each LED panel could have its own sweep gas source28 and collection chamber 22.

A sweep gas source 28 is provided to force evolved CO₂ into thecollection chamber 22 and to prevent CO₂ from being reabsorbed into theMEA solution. The sweep gas could be a gas which does not readily absorbinto MEA and which is not harmful to have as an affluent fraction. Nonreactive gases such as nitrogen, argon, or helium could be used as thesweep gas. An absorption chamber 54 is provided for the purpose ofensuring optimum exposure of the applicable UV wavelength to thescrubber solution. CO₂-lean MEA enters the absorption chamber at 56 andexits the absorption chamber at 58 for routing to the CO₂ separationprocess.

The disclosed technology utilizes a photolytic separation processemploying LED arrays to generate UV photons to desorb or strip CO₂—fromMEA carbamate as a result of using aqueous MEA for Carbon dioxidecapture. The disclosed technology removes as much as 90% of the CO₂ withless than a 45% increase in the COE. The disclosed technology will havea strong impact on lowering the COE of the current state-of-the-artMEA-carbon capture technology.

Cooper et al. have shown that it is possible to absorb 97% of the UVgenerated for cleaning swimming pool water. The disclosed technologyfrees up to 90% CO₂ from (MEA)₂-CO₂ in 20 or 30% aqueous MEA scrubbers.A thin liquid film photochemical reactor, is one preferred embodimentthat may be used in a successfully large scale process to evaluatereleased CO₂.

With the appropriate design, liquid film thickness can be adjusted forefficient absorption of UV radiation by the CO₂-rich MEA mixture.Further, the impact of flow rate, and contact time on the separation ofCO₂ from (MEA)₂-CO₂ will be studied. UV transparent quartz glass will beused to construct the reactor surface in order to achieve maximumabsorption on photon energy by the process. A counter flow of sweep gascan be used to remove CO₂ generated by exposure of CO₂-rich MEA to UV.

Table 2 lists frequencies (or wavelengths) presently preferred fordissociating bonds of the pollutants listed.

TABLE 2 UV maximum absorption wavelength selected Bonds in (MEA)₂-CO₂,(MEA)-SO_(x), SO_(x), NO_(x), etc Maximum Wavelength Chemical Bond forDissociation [nm] N—H (NH) 336.4 N—O 595.6 S—N 248.6 S—O 240.3(MEA)₂-CO₂ → 2MEA + CO₂ 350-420

One of the significant advantages of UV AlInGaN LEDs over high pressurelamps is that they generate UV radiation over a very narrow spectralband, as illustrated in FIGS. 10 and 11. As FIG. 10 shows, UV LEDs havea relatively narrow unfiltered spectral output, typically with a FWHM ofonly 20 nm. In comparison, the spectral output from a mercury bulb (FIG.11) contains a series of several peaks throughout the UV to visiblespectral region. As a result, such bulbs require a filter sleeve toremove the unwanted peaks. This represents a direct energy loss thatincreases the input power to the lamp necessary to obtain the requisiteenergy density for the photolytic process. The disclosed technology isan improvement over this use of energy by utilizing LEDs with a narrowspectral output, but one which is selected for effectiveness for aparticular pollutant such as CO₂, SO_(x) or NO_(x), as examples.

The disclosed technology may be operated as a batch process, and also asa continuous process.

The operation of the photochemical reactor and the method of its use(FIG. 11) involve: (i) production of molCO₂/molMEA and UV analysis ofspecific concentration; (ii) valve off the inlet and outlet to isolateliquid mixture in the thin film photochemical reactor; (iii) turn ONnitrogen (N₂) sweep gas flow to begin to create homogeneous orheterogeneous bubbles; (iv) switch ON the LED UV generator; (v) applymonochromatic UV irradiation at =200-420 nm range from LED UV generator;(vi) monitor the change in amine and carbamate concentrations (in thecase of CO₂ removal) in the reactor as a function of time by analysis ofgrab samples by UV spectrophotometer; (vii) real-time quantitativeanalysis of CO₂ production by online FTIR spectroscopy; (viii) determinethe presence of byproducts in the liquid phase by UV analysis; and inthe gas phase by FTIR; (ix) begin real-time online analysis of CO₂ inthe N₂ sweep gas; and (x) record UV spectrum of liquid grab samples fromthe process vent, over varying periods of operation.

The method of the disclosed technology includes the steps of selectingthe optimum LED frequency output and working distance for a selectedeffluent pollutant, such as CO₂, SO_(x), or NO_(x), mixing a process(coal power plant, internal combustion engine) effluent with anabsorption media (such as MEA) for absorption of the pollutant, passingthe pollutant rich media over at least one LED UV source, forirradiation and release of the pollutant as a gas, sweeping the evolvedgas into a collection system with a sweep gas, to prevent re-absorptionof the pollutant into the media, collecting and/or analyzing thepollutant gas, and returning MEA to the absorption cycle

While certain exemplary embodiments are shown in the Figures anddescribed in this disclosure, it is to be distinctly understood that thepresently disclosed inventive concept(s) is not limited thereto but maybe variously embodied to practice within the scope of the followingclaims. From the foregoing description, it will be apparent that variouschanges may be made without departing from the spirit and scope of thedisclosure as defined by the following claims.

1. A method for removal of pollutants from effluent streams, comprisingthe steps of: passing gaseous effluent streams through an absorptivemedia for absorption of pollutant oxides into said absorptive media;routing said absorptive media with absorbed pollutant oxides to a UVreaction chamber; irradiating said absorptive media with absorbedpollutant oxides with LED generated UV at a wavelength selected formaximum energy efficiency of release of pollutant oxides from saidabsorptive media, with said pollutant oxides exiting said media as agas; capturing gaseous pollutant oxides for compression and disposal;returning said absorptive media with pollutant oxides removed to contactwith said gaseous effluent streams.
 2. The method of removal ofpollutants of claim 1 in which the method further comprises the step ofreleasing carbon dioxide as the pollutant oxide.
 3. The method ofremoval of pollutants of claim 1 in which the method further comprisesthe step of releasing sulfur dioxides as the pollutant oxide.
 4. Themethod of removal of pollutants of claim 1 in which the method furthercomprises the step of releasing nitrous oxide as the pollutant oxidesaid pollutant oxide.
 5. The method of removal of pollutants of claim 1in which the method further comprises using an absorptive media selectedfrom the list consisting of monoethanolamine, ammonia, and othersuitable amines or scrubbers.
 6. The method of removal of pollutants ofclaim 1 in which the method further comprises the step of using LEDgenerated UV is confined to a frequency band restricted to less than 50nm in width.
 7. The method of removal of pollutants of claim 6 in whichthe method further comprises the step of using LED generated UV isproduced between 200 to 420 nm.
 8. The method of removal of pollutantsof claim 6 in which the method further comprises the step of using LEDgenerated UV is produced between 260 to 400 nm.
 9. The method of removalof pollutants of claim 6 in which the method further comprises the stepof using LED generated UV is produced between 300 to 420 nm.
 10. Themethod of removal of pollutants of claim 6 in which the method furthercomprises the step of using LED generated UV is produced between 380 to400 nm.
 11. The method of claim 1 in which the method further comprisesthe step of using an effluent stream comprised of effluent from a powergeneration plant.
 12. The method of claim 1 in which the method furthercomprises the step of using an effluent stream comprised of effluentfrom an internal combustion engine.
 13. A method for removal ofpollutants from effluent streams, comprising the steps of: passinggaseous power plant effluent streams through an absorptive media forabsorption of carbon dioxide into said absorptive media; routing saidabsorptive media with absorbed carbon dioxide to a UV reaction chamber;irradiating said absorptive media with absorbed carbon dioxide with LEDgenerated UV at a wavelength selected for maximum energy efficiency ofrelease of carbon dioxide from said absorptive media, with said carbondioxide exiting said media as a gas; capturing gaseous carbon dioxidefor compression and disposal; returning said absorptive media withcarbon dioxide removed to contact with said gaseous effluent streams.14. A method for removal of pollutants from effluent streams, comprisingthe steps of: passing gaseous power plant effluent streams through anabsorptive media for absorption of sulfur dioxide into said absorptivemedia; routing said absorptive media with absorbed sulfur dioxide to aUV reaction chamber; irradiating said absorptive media with absorbedsulfur dioxide with LED generated UV at a wavelength selected formaximum energy efficiency of release of sulfur dioxide from saidabsorptive media, with said sulfur dioxide exiting said media as a gas;capturing gaseous sulfur dioxide for compression and disposal; returningsaid absorptive media with sulfur dioxide removed to contact with saidgaseous effluent streams.
 15. A method for removal of pollutants fromeffluent streams, comprising the steps of: passing gaseous power planteffluent streams through an absorptive media absorption of nitrous oxideinto said absorptive media; routing said absorptive media with nitrousoxide to a UV reaction chamber; irradiating said absorptive media withabsorbed nitrous oxide with LED generated UV at a wavelength selectedfor maximum energy efficiency of release of nitrous oxide from saidabsorptive media, with said nitrous oxide exiting said media as a gas;capturing gaseous nitrous oxide for compression and disposal; returningsaid absorptive media with nitrous oxide dioxide removed to contact withsaid gaseous effluent streams.
 16. The method of removal of pollutantsof claim 1 in which the method further comprises the step of releasingcarbon dioxide as the pollutant oxide.
 17. The method of removal ofpollutants of claim 1 in which the method further comprises the step ofreleasing sulfur dioxides as the pollutant oxide.
 18. The method ofremoval of pollutants of claim 1 in which the method further comprisesthe step of releasing nitrous oxide as the pollutant oxide saidpollutant oxide.
 19. The method of removal of pollutants of claim 1 inwhich the method further comprises using an absorptive media comprisedof monoethanolamine.
 20. The method of removal of pollutants of claim 1in which the method further comprises the step of using LED generated UVis confined to a frequency band restricted to less than 50 nm.
 21. Themethod of removal of pollutants of claim 6 in which the method furthercomprises the step of using LED generated UV is produced between 200 to420 nm.
 22. The method of removal of pollutants of claim 6 in which themethod further comprises the step of using LED generated UV is producedbetween 260 to 400 nm.
 23. The method of removal of pollutants of claim6 in which the method further comprises the step of using LED generatedUV is produced between 300 to 420 nm.
 24. The method of removal ofpollutants of claim 6 in which the method further comprises the step ofusing LED generated UV is produced between 380 to 400 nm.
 25. The methodof claim 1 in which the method further comprises the step of using aneffluent stream comprised of effluent from a power generation plant. 26.The method of claim 1 in which the method further comprises the step ofusing an effluent stream comprised of effluent from an internalcombustion engine.